Tolerance rings are used in various assembly applications, such as in hard disk drives. Hard disk drives typically include a base and a rotary actuator that is attached to the base and that rotates through a fixed angular range. The rotary actuator positions one or more read heads relative to data tracks on a spinning magnetic disk. To facilitate angular rotation, the rotary actuator typically includes a bore into which a pivot bearing cartridge is inserted and affixed. The rotary actuator typically comprises aluminum or an alloy thereof, although alloys of magnesium and beryllium also have been used for this purpose, and the pivot bearing cartridge is typically a stainless steel component, although other materials such as ceramics have been proposed.
There are various methods in the art to attach the pivot bearing cartridge into the actuator bore. For example, the pivot bearing cartridge may be affixed within the actuator bore by an adhesive or by use of a snap ring or C-clip. Another way of affixing the pivot bearing cartridge within the actuator bore is to take up the radial space or tolerance between the pivot bearing cartridge and the actuator bore with a resilient tolerance ring (also known as an interference band). The tolerance ring undergoes incomplete radial compression between the pivot bearing cartridge and the actuator bore so as to provide a residual radial preload force between the two components that practically affixes one to the other.
However, in order to achieve higher data capacities in disk drives, the track density (typically expressed in data tracks per inch) on magnetic disks has been increased. This increase has made it more challenging to control the actuator so as to quickly and precisely position the read head(s) over desired data tracks. In certain disk drives that employ tolerance rings to affix the pivot bearing within the actuator bore, the actuator rotational friction within its limited angular range may be undesirably non-uniform. Disk drives that employ tolerance rings may also suffer from poor pivot bearing cartridge centering within the actuator bore and/or undesirable dynamic resonance characteristics of the actuator assembly. Such issues may exacerbate the difficulty in quickly and precisely controlling the actuator. Hence, there is a need in the art for a tolerance ring that may improve the performance of modern hard disk drive devices and/or other precision devices.